Make columns configurable

[caarmen]

We may not be interested in all columns for a given project.

Not sure what would be simpler as a first iteration, but I see a few possibilities:

• save a global preference of which columns to show, which will apply to everybody (stored in the server db)
• save the preference of which columns to show, based on each user (browser cookie perhaps, as we don't have a notion of "users" at this point), or maybe as url parameters